The present application is related generally to systems and methods for controlling railway systems and, in particular, to a system and method for scheduling and controlling a periodic train service using unmanned locomotives.
It has long been desired to reduce the cost of operating railway systems by reducing or eliminating the number of persons needed to control a train while maintaining a very high degree of safety. A small measure of success has been obtained in automatic control of trains (i.e., operation of trains without active human control) on small, fixed route railway lines, usually carrying passengers. For example, the Bay Area Regional Transit ("BART") system in San Francisco and the inter-terminal passenger shuttle systems at various airports such as Orlando and Tampa Bay utilize automatic train control systems to operate passenger railway systems over a relatively small geographic territory and utilize service which is generally periodic, i.e., a train shuttles between one terminal and another (or between one station and another) on a fixed and generally unvarying schedule, with fixed guideways.
Generally, in such prior art systems, the schedule of operation of the trains is fixed, often months in advance and may therefor be set in such a way to avoid or reduce the effect of conflicts in the use of track resources. For example, fixed, periodic trains can be scheduled to avoid two trains vying for the use of the same track at the same time.
Another general characteristic of many prior art automatic train control systems is the limited number of differences in the compositions of the trains. Usually, for example, every train on a particular segment of track (or on a "line") has a similar, if not an identical, composition, e.g., each train is composed of six passenger cars during non-rush hour and of ten passenger cars during rush hour operation. Because of the limited number of differences among the compositions of such trains, control systems which utilize fixed block methods of control are reasonably efficient. In fixed block control, the track layout is divided into track segments having lengths related to the stopping distances of the trains which operate over them. Trains are then controlled to avoid each other by separating them by a determined number of blocks. For example, in one such prior art system, a following train is permitted to run as long as it is no closer than three "blocks" from the train in front of it. If the distance between the trains is reduced to three blocks, the following train may be forced to slow its speed; if the distance is reduced to two blocks, the following train performs a full service braking; and if the distance is reduced to a single block, the following train performs an emergency stop. While such a control scheme may be reasonable when all trains have a like stopping distance, such a control scheme may be very inefficient if the trains being controlled vary considerably in stopping distance. For example, a relatively short, unloaded train may be able to stop in a much shorter distance than a relatively long, loaded train. In a typical fixed block system as used in many prior art automatic train control systems, the length of the block is usually set to a length relative to the stopping distance of the longest, heaviest train expected to be run on the track layout. Shorter, lighter or better braking trains running on such a fixed block system are controlled by such a system to follow at a distance much greater than required to stop safely. Such additional and unneeded distance between following trains wastes the track layout, permitting fewer trains to use a given track layout in a given amount of time. For a further explanation of the difficulties of fixed block systems, refer to the Matheson et al. U.S. Pat. No. 5,623,413, issued Apr. 22, 1997, entitled "Scheduling System and Method", and having some inventors in common with the present application.
In all railway systems, safety of operation is of paramount concern. Prior art systems and the present invention share a characteristic that they are designed to be "vital", i.e., portions of the control system, the failure of which could cause an unauthorized (and potentially dangerous) movement of a train, are made redundant and/or fail safe. Accordingly, most prior art automatic train control systems utilize train-centric or wayside-centric control schemes which permit movement of trains, manned or unmanned, only with respect to relatively local conditions which can be monitored and/or controlled by equipment carried by the train and/or by wayside units. For example, in the fixed block control system described above, the vital control apparatus may consist primarily of redundant wayside detection and authorization apparatus along the entirety of the track layout. This apparatus may by configured to control nearby fixed blocks of track by detecting the presence of trains thereon, the direction of switches, and the status of other trackside equipment (tunnel doors, hot box detectors, etc.) within the nearby control area. Logic circuits (often in trackside bungalows) are designed to implement the block movement rules discussed above and to signal train operators (or automatic equipment onboard a locomotive) to cause the train to proceed only when the track ahead is safe. The use of wayside-centric fixed block control has been successful in relatively small size track layouts with relatively similar trains operating thereon. However, when a relatively large track layout is involved, the cost of the vital (usually redundant) wayside equipment throughout the track layout can be considerable. In addition, purely local control of train operation such as carried out by typical wayside-centric equipment makes it extremely difficulty to optimize the throughput of trains across the entire track layout. Decisions as to train movement which are made with only a local perspective may cause significant ripple effects on other trains operating in the track layout. For example, if a particular train is placed on a siding to avoid an on-coming train on a single track system, the stopped train may fall behind its schedule causing other, subsequent meets which had been planned to be missed and throwing an entire schedule out of kilter whereas the schedule might have been saved if the train which the local wayside-centric control permitted to pass without stopping had been sent to the siding instead.
Prior art unmanned train control systems typically used locomotive-centric or wayside-centric logic circuits to determine vital control operation. In either situation, the local nature of the control decisions could have a ripple effect on other trains in the track layout as described immediately above.
The typical automatic train control system controls the operation of the unmanned train by communication sent through wayside units to the train. Often, these train control systems assign the train a block of track in which the train is authorized to run and assign a fixed speed for any given block. Moreover, typical automatic train control systems are routed and controlled using a fixed set of priorities and routes resulting in only a minimal amount of flexibility to work around problems. These systems do not have the predictive intelligence to plan beyond the next few blocks as monitored by the signal system. Other movement planners establish a long-term plan and rely upon human intervention when deviations to the plan become necessary.
The present invention incorporates centralized control of both the vehicles and the track resources. It accomplishes this centralized control by utilizing a flexible reactive movement planner which will continuously adjust train routes and controls so that system throughput is optimized. One advantage of this look ahead planner is that intelligent decisions can be made due to the collection of real time data as well as the use of predictive algorithms which are able to estimate upcoming requirements.
Many prior art automatic train control systems use a predetermined speed which may be set for each block, according to local conditions. While such a control scheme may permit the train to pass through a particular block at the highest speed, the train may arrive at the next or subsequent blocks ahead of the time when the block is available (prior to when a track resource within a block is available). Most prior art automatic train control systems handle this situation by merely commanding the train to stop and wait until the block or track resource becomes available. Such stopping and restarting of trains is generally detrimental, as wheel wear, wheel sliding, and track wear are generally increased substantially during train stopping or starting. Likewise, train components such as the transmission and similar tractive components wear substantially more when stopping or starting. In contrast to many systems in the prior art, the present invention determines and commands the trains operating within its purview to follow a specified speed trajectory along its route which can be optimized to increase the throughput of trains through the track layout and to adjust the speed of the trains to obtain needed pacing between trains or between a train and a track resource without the need for unnecessary braking.
One of the benefits of the present system is the improved throughput over the rail that results from planning efficient train movements. Unlike the typical movement planner which establish a long term plan but can not dynamically adjust the plan, the present invention can rapidly react to changes in predicted needs and create a new movement plan within one second. The reactive movement planner constantly receives train position and velocity along with switch status and can update the movement plan in order to reflect actual performance on the rails of each vehicle. Replanning of the train movement may be accomplished frequently in order to stay current with the activities on the railway system.
In the present invention, all data received from the vehicles and the wayside interface units may be stored in a database located at the centralized control station. When a replan is required, the reactive movement plan can access the most current data as reflected in the database in order to plan the optimal movement of the vehicles and establish train routes and estimated time of arrival at selected control points. Since the planner is adjusting the train routes at regular, very short intervals (approximately once per second) it can adapt quickly to changing conditions. In many cases, the new plan will be identical to the former plan except that it has been extended for an additional second because no unexpected changes will have occurred. The central control station converts the movement plan developed by the reactive movement planner into commands for locomotives and for the controlling of the wayside resources. The central control station may also continuously poll the locomotives for status and location and the wayside interface units for the status of track resources so that it has the most current status.
The present invention incorporates the ability to selectively lockout or remove sections of the railway and associated wayside resources from being available to the movement planner. Manual lockouts are a critical function to the present invention because they are the primary method of protecting work crews and maintenance equipment which may occupy the track. Manual lockouts may be initiated locally at a wayside interface unit or from the central control station. To lock out a section of track for repair or any other use, the section must be clear of existing traffic. Once locked out, the section is no longer available to the movement planner to implement the movement plan and no new traffic will be allowed to enter.
As an additional safety feature, each wayside interface unit may contain up to two emergency shutdown switches. Activation of one of these switches will cause all trains within a programmed portion of the railway system or all trains within the entire railway system to stop until the condition is cleared. The area controlled by each switch is not limited to areas surrounding the wayside interface unit and will be programmed during initial system configuration. When an emergency switch is activated, the central control station will log the time and location of this event. These switches are meant to be used in emergency situations only since some or all of the railway system operation will be shut down until the problem is cleared. Once the emergency condition is cleared the system will restart and continue normal operations, adjusting for any changes required due to the system shutdown.
Accordingly, it is an object of the present invention to provide a novel method of automatic train control utilizing centralized control of the trains and the wayside resources.
It is another object of the present invention to provide a novel method to reduce brake maintenance and prevent rail abuse.
It is yet another object of the present invention to provide a novel method of improving throughput over a railway system by planning efficient train movements.
It is still another object of the present invention to provide a novel system and method for providing vital control of train movement while reducing required redundant wayside units throughout a track layout.
It is still another object of the present invention to provide a novel method of increasing safety through centralized vital control of train movement.
it is yet another object of the present invention to provide a novel method to detect and react to constraints including broken rail, weather, speed restrictions, etc. and still optimize train movement.
It is still another object of the present invention to provide a novel method to spot a train precisely repeatedly for unloading operations.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.